With the development of genetic engineering technology, it has become possible to use antibodies such as immunoglobulins, monoclonal antibodies and humanized antibodies as pharmaceutical products. To supply them in stable amounts, it is necessary to establish preparation conditions and storage conditions under which the structure and activity of the antibodies can be retained.
When proteins are stored in high concentration solutions, they normally suffer deterioration such as the formation of insoluble aggregates, which must be prevented. Especially, antibody formulations have the disadvantage that they tend to form multimers leading to insoluble aggregates during storage in solutions.
For example, we found that anti-IL-6 receptor antibodies have a therapeutic effect on immature myeloma cells (JPA HEI 8-99902) and succeeded in mass-producing a reshaped humanized antibody, hPM-1 antibody, as an anti-IL-6 receptor antibody, and we have tried to formulate this purified anti-IL-6 receptor antibody into pharmaceutical products. The humanized anti-IL-6 receptor antibody is an unstable protein liable to physical or chemical changes such as association or aggregation under the stresses of filtration, concentration, heat and light for removing viruses and other microbials during purification processes.
When antibodies are to be obtained by genetic engineering techniques, antibody-producing cells are cultured in bulk and purified to give an antibody-containing solution, which is then stored frozen and thawed before formulation. However, the antibody content remaining in such a solution decreased as antibody dimers or insoluble particles were formed during repeated freeze/thaw cycles or antibodies were degraded to form degradation products during long-term storage.
Many efforts have been made to provide a method for storing proteins in solutions, and a stabilization effect was found by adding polymers including proteins such as human serum albumin or purified gelatin or oligomers such as polyols, amino acids and surfactants as stabilizers for preventing chemical or physical changes. However, the addition of biopolymers such as proteins as stabilizers was inconvenient, e.g. it required a very complicated step for eliminating contaminants such as viruses and prions. As to the addition of oligomers, it should preferably be minimized.
Freeze-dried antibody formulations stabilized with sugars or amino sugars, amino acids and surfactants have also been reported (JPA HEI2001-503781).
However, stable antibody-containing solution formulations have been sought because of great demands for easy-to-use solution formulations that may not be dissolved/reconstituted before use.